From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49620) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Stio0-0004Ou-Nz for qemu-devel@nongnu.org; Tue, 24 Jul 2012 13:21:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Stinv-0000V4-Et for qemu-devel@nongnu.org; Tue, 24 Jul 2012 13:21:56 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:53639) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Stinv-0000Fl-8d for qemu-devel@nongnu.org; Tue, 24 Jul 2012 13:21:51 -0400 Received: by mail-pb0-f45.google.com with SMTP id ro12so12773613pbb.4 for ; Tue, 24 Jul 2012 10:21:51 -0700 (PDT) Sender: fluxion From: Michael Roth Date: Tue, 24 Jul 2012 12:20:44 -0500 Message-Id: <1343150454-4677-13-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1343150454-4677-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1343150454-4677-1-git-send-email-mdroth@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 12/22] qom-fuse: workaround for truncated properties > 4096 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: aliguori@us.ibm.com, quintela@redhat.com, owasserm@redhat.com, yamahata@valinux.co.jp, pbonzini@redhat.com, akong@redhat.com, afaerber@suse.de We currently hard-code property size at 4096 for the purposes of getattr()/stat()/etc. For 'state' properties we can exceed this easily, leading to truncated responses. Instead, for a particular property, make it max(4096, most_recent_property_size * 2). This allows some head-room for properties that change size periodically (numbers, strings, state properties containing arrays, etc) Also, implement a simple property cache to avoid spinning on qom-get if an application reads beyond the actual size. This also allows us to use a snapshot of a single qom-get that persists across read()'s. Old Cache entries are evicted as soon as we attempt to read() from offset 0 again. Signed-off-by: Michael Roth --- QMP/qom-fuse | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/QMP/qom-fuse b/QMP/qom-fuse index 5c6754a..bd43f29 100755 --- a/QMP/qom-fuse +++ b/QMP/qom-fuse @@ -26,6 +26,7 @@ class QOMFS(Fuse): self.qmp.connect() self.ino_map = {} self.ino_count = 1 + self.prop_cache = {} def get_ino(self, path): if self.ino_map.has_key(path): @@ -67,12 +68,16 @@ class QOMFS(Fuse): if not self.is_property(path): return -ENOENT - path, prop = path.rsplit('/', 1) - try: - data = str(self.qmp.command('qom-get', path=path, property=prop)) - data += '\n' # make values shell friendly - except: - return -EPERM + # avoid extra calls to qom-get by using cached value when offset > 0 + if offset == 0 or not self.prop_cache.has_key(path): + directory, prop = path.rsplit('/', 1) + try: + resp = str(self.qmp.command('qom-get', path=directory, property=prop)) + self.prop_cache[path] = resp + '\n' # make values shell friendly + except: + return -EPERM + + data = self.prop_cache[path] if offset > len(data): return '' @@ -111,13 +116,18 @@ class QOMFS(Fuse): 0, 0)) elif self.is_property(path): + directory, prop = path.rsplit('/', 1) + try: + resp = str(self.qmp.command('qom-get', path=directory, property=prop)) + except: + return -ENOENT value = posix.stat_result((0644 | stat.S_IFREG, self.get_ino(path), 0, 1, 1000, 1000, - 4096, + max(len(resp) * 2, 4096), 0, 0, 0)) -- 1.7.9.5